1. Field of the Invention
The present invention relates to a piston support structure of a reciprocating compressor, and more particularly, to a piston support structure of a reciprocating compressor which is positioned on both sides of a piston for receiving the linear reciprocating driving power of a reciprocating motor and compressing a gas while being in a linear reciprocating motion in the compression space of a cylinder. The piston support structure extends the durability of a resonant spring for elastically supporting the piston.
2. Description of the Background Art
In general, compressors for compressing fluid can be divided into rotary compressors, scroll compressors, and reciprocating compressors according to the respective method for compressing a refrigerant gas.
As shown in FIG. 1, an example of a reciprocating compressor includes a container 10 and a reciprocating motor 20 for generating linear reciprocating power loaded in the container 10. The compressor also includes a hind frame 30 and a central frame 40 for supporting both sides of the motor 20, a front frame 50 continuously combined with the central frame 40, a cylinder 60 fixedly combined with the front frame 50 so as to be separated from the reciprocating motor by a predetermined distance, and a piston 70 connected to the reciprocating motor 20 and inserted into the cylinder 60 to be in a linear reciprocating motion in the cylinder 60. The piston 70 also receives the linear reciprocating driving power of the reciprocating motor 20. The compressor also includes a valve unit 80 combined with the cylinder 60 and the piston 70. The valve unit 80 draws up a gas into the cylinder 60 and discharges the gas into the outside of the cylinder 60 due to the pressure difference generated by the reciprocation motion of the piston. A resonant spring unit 90 for elastically supporting the linear reciprocating motions of the reciprocating motor 20 and the piston 70 is also provided.
The reciprocating motor 20 includes a cylindrical outer stator 21 fixedly combined with the hind frame 30 and the central frame 40, an inner stator 22 inserted into the outer stator 21 to be separated from the outer stator 21 by a predetermined distance, a winding coil 23 combined with the outer stator 21 inside the outer stator 21, and a moving magnet A inserted between the outer stator 21 and the inner stator 22 to be in the linear reciprocating motion.
The moving magnet A includes a cylindrical magnet holder 24 and a plurality of permanent magnets 25 combined with the magnet holder 24 and separated from each other by a predetermined distance. The magnet holder 24 is connected to one side of the piston 70.
The valve unit 80 includes a discharge cover 81 for covering the compression space P of the cylinder 60 and a discharge valve 82 located in the discharge cover 81. The discharge valve 82 opens and closes the compression space P of the cylinder 60. The valve unit 80 also includes a valve spring 83 for elastically supporting the discharge valve 82 and a suction valve 84 combined with the end of the piston 70. The suction valve 84 opens and closes a suction channel F formed in the piston 70.
The refrigerant gas is drawn up into a suction pipe 1. The compressed refrigerant gas is discharged into a discharge pipe 2. The operation of the conventional reciprocating compressor will now be described in greater detail hereinafter.
When power is supplied to the reciprocating motor 20, current flows through the winding coil 23. The moving magnet A, including the permanent magnets 25, is in a linear reciprocating motion due to a mutual operation between the flux formed in the outer stator 21 and the inner stator 22 and the permanent magnets 25 due to the current that flows through the winding coil 23.
The linear reciprocating driving power of the moving magnet A is transmitted to the piston 70. Accordingly, the piston 70 has a linear reciprocating motion with a stroke that is the distance between a top dead center and a bottom dead center in the compression space P formed in the cylinder 60. The valve unit 80 operates at the same time as the piston 70. Accordingly, the refrigerant gas is sucked up into the compression space P of the cylinder 60, is compressed, and is discharged into the outside of the cylinder 60. The above processes are repeated.
The resonant spring unit 90 stores the linear reciprocating motion energy of the reciprocating motor 20 as elastic energy and emits the elastic energy. At the same time, the resonant spring unit 90 causes a resonant motion.
As shown in FIG. 2, the resonant spring unit 90, which causes the resonant motion with respect to the linear reciprocating motion of a driving portion including the moving magnet A of the reciprocating motor 20 and the piston 70 combined with the moving magnet A, is combined with one side of the piston 70. A spring supporter 91 formed to be bent so as to have a predetermined area is positioned between the front frame 50 and the central frame 40.
A first resonant spring 92 is inserted between the front frame 50 and the spring supporter 91. A second resonant spring 93 is inserted and combined between the spring supporter 91 and the central frame 40.
The elastic modulus of the first resonant spring 92 is the same as the elastic modulus of the second resonant spring 93. The first resonant spring 92 is combined with the second resonant spring 93 in a state where the first resonant spring 92 and the second resonant spring 93 are compressed to uniform lengths, respectively.
The first resonant spring 92 and the second resonant spring 93 are combined with each other so that the initial position f of the end of the piston 70 is moved from the center c between the maximum top dead center b and the maximum bottom dead center a toward the end d of the cylinder 60 by a predetermined distance, e.g., a movement distance e, considering gas spring force during compression.
Also, in the resonant spring unit 90, when the piston 70 moves toward the top dead center, the first resonant spring 92 contracts and the second resonant spring 93 is extended to be longer than the initial setting length. When the piston 70 moves toward the bottom dead center, the first resonant spring 92 is extended to be longer than the initial setting length and the second resonant spring contracts. The moving magnet A and the piston 70 are elastically supported by repeating the above processes.
However, according to the conventional reciprocating compressor, during the process of compressing the refrigerant gas with the reciprocating motion of the piston 70 in the compression space P in the cylinder 60, the gas spring force due to the increase in the pressure of the refrigerant gas compressed in the compression space P of the cylinder 60 is applied to the piston 70. Accordingly, since the end of the piston 70 is in the linear reciprocating motion between the top dead center and the bottom dead center in a state where the end of the piston 70 is moved from the initial position f positioned during setting toward the center position c of the maximum top dead center b and the maximum bottom dead center a, the compressing displacement of the second resonant spring 93 is larger than the compressing displacement of the first resonant spring 92.
Accordingly, the first resonant spring 92 receives less stress than the set stress, and the second resonant spring 93 receives more significant stress than the set stress. Therefore, the fatigue endurance of the second resonant spring 93 deteriorates to shorten the durability of the second resonant spring 93.
Therefore, an object of the present invention is to provide a piston support structure for a reciprocating compressor which is positioned on both sides of a piston for receiving the linear reciprocating driving power of a reciprocating motor and compressing a gas while being in a linear reciprocating motion in the compression space of a cylinder.
An object of the present invention is to provide a piston support structure for extending the durability of a resonant spring for elastically supporting the piston.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a piston support structure of a reciprocating compressor comprising a piston receiving linear reciprocating driving power generated by a reciprocating motor and being in a linear reciprocating motion in a compression space formed in a cylinder and a first resonant spring and a second resonant spring positioned on both sides of the piston, the first resonant spring and the second resonant spring for elastically supporting the linear reciprocating motion of the piston. The spring constant of the second resonant spring opposite to the first resonant spring is larger than the spring constant of the first resonant spring positioned on the side of the compression space of the cylinder.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
FIG. 1 is a vertical sectional view of a conventional reciprocating compressor of the background art;
FIG. 2 is a partial sectional view showing a piston support structure of the conventional reciprocating compressor of the background art;
FIG. 3 is a vertical sectional view showing a reciprocating compressor including a piston support structure of a reciprocating compressor according to the present invention;
FIG. 4 is a sectional view showing the piston support structure of the reciprocating compressor according to the present invention;
FIG. 5 is a sectional view showing another modification of the piston support structure of the reciprocating compressor according to the present invention;
FIG. 6 is a sectional view showing another modification of the piston support structure of the reciprocating compressor according to the present invention; and
FIG. 7 is a sectional view showing another modification of the piston support structure of the reciprocating compressor according to the present invention.